Light emitting device with light path changing structure

ABSTRACT

The inventive concept provides light emitting devices and methods of manufacturing a light emitting device. The light emitting device may include a transparent substrate including a first region and a second region, a first transparent electrode disposed on a first surface of the transparent substrate, a second transparent electrode facing and spaced apart from the first transparent electrode, an organic light emitting layer disposed between the first and second transparent electrodes, an assistant electrode disposed between the first and second transparent electrodes and selectively masking the second region, and a light path changing structure disposed on a second surface of the transparent substrate and selectively masking the second region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 to Korean Patent Application No. 10-2011-0073512, filed onJul. 25, 2011, the entirety of which is incorporated by referenceherein.

BACKGROUND

The inventive concept relates to light emitting devices and methods ofmanufacturing the same and, more particularly, to organic light emittingdevices and methods of manufacturing the same.

An electronic industry, which communicates information to people fromvarious devices, is very attractive in a modern industry societydeveloped to an information age. This tendency is expected to bemaintained for quite a long time.

Particularly, in a display field corresponding to a man-machineinterface, various researches have been conducted for displayingsophistication and color that can satisfy visual sense of people and becloser to nature.

Generally, a display is widely used to a television, a monitor, and amobile phone. However, light, wide, fast, and high resolution displayshave been increasingly demanded with the development of a technique.

Additionally, the display industry pursues small size, lightness, andthinness of the displays by using a thin film and demands the highresolution of the displays. Organic light emitting devices have beenstudied for realizing the displays having the high resolution.Particularly, researches have been conducted for improving lightextraction efficiency and uniformity of the organic light emittingdevices.

SUMMARY

Embodiments of the inventive concept may provide light emitting devicescapable of improving light extraction efficiency and uniformity.

Embodiments of the inventive concept may also provide methods ofmanufacturing the light emitting device.

According to some embodiments of the inventive concepts, a lightemitting device may include: a transparent substrate including a firstregion and a second region; a first transparent electrode disposed on afirst surface of the transparent substrate; a second transparentelectrode facing and spaced apart from the first transparent electrode;an organic light emitting layer disposed between the first and secondtransparent electrodes; an assistant electrode disposed between thefirst and second transparent electrodes, the assistant electrodeselectively masking the second region; and a light path changingstructure disposed on a second surface of the transparent substrate, thelight path changing structure selectively masking the second region.

In some embodiments, the light path changing structure may include amicro lens array.

In other embodiments, the light path changing structure may include apattern formed at the transparent substrate in the second region.

In still other embodiments, the pattern formed at the transparentsubstrate may have concave-curved surfaces.

In yet other embodiments, the light path changing structure may includean optical dispersion layer.

In yet still other embodiments, the optical dispersion layer may includenano-particles.

In yet still other embodiments, the assistant electrode may include ametal which light does not pass through and which has a resistance lowerthan that of the first transparent electrode.

According to other embodiments of the inventive concepts, a method ofmanufacturing a light emitting device may include: forming a firsttransparent electrode on a first surface of a transparent substrateincluding a first region and a second region;

forming an assistant electrode selectively masking the second region onthe first transparent electrode; forming an organic light emitting layercovering the first transparent electrode and the assistant electrode;forming a second transparent electrode on the organic light emittinglayer; and forming a light path changing structure selectively maskingthe second region on a second surface of the transparent substrate.

In some embodiments, forming the light path changing structure mayinclude: fixing a detachable micro lens array on a transfer substrate;and bonding the micro lens array to the second surface of thetransparent substrate in the second region.

In other embodiments, forming the light path changing structure mayinclude: selectively etching the second surface of the transparentsubstrate in the second region to form a pattern includingconcave-curved surfaces.

In still other embodiments, forming the light path changing structuremay include: forming an optical dispersion layer on the second surfaceof the transparent substrate in the second region.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive concept will become more apparent in view of the attacheddrawings and accompanying detailed description.

FIG. 1 is a plan view illustrating a light emitting device according toembodiments of the inventive concept;

FIG. 2A is a cross-sectional view illustrating a light emitting deviceaccording to some embodiments of the inventive concept;

FIG. 2B is a cross-sectional view illustrating a path of light generatedfrom a light emitting device according to some embodiments of theinventive concept;

FIG. 3A is a cross-sectional view illustrating a light emitting deviceaccording to other embodiments of the inventive concept;

FIG. 3B is a cross-sectional view illustrating a path of light generatedfrom a light emitting device according to other embodiments of theinventive concept;

FIG. 4A is a cross-sectional view illustrating a light emitting deviceaccording to still other embodiments of the inventive concept;

FIG. 4B is a cross-sectional view illustrating a path of light generatedfrom a light emitting device according to still other embodiments of theinventive concept;

FIGS. 5A to 5G are cross-sectional views illustrating a method ofmanufacturing a light emitting device according to some embodiments ofthe inventive concept;

FIGS. 6A to 6D are cross-sectional views illustrating a method ofmanufacturing a light emitting device according to other embodiments ofthe inventive concept; and

FIGS. 7A and 7B are cross-sectional views illustrating a method ofmanufacturing a light emitting device according to still otherembodiments of the inventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The inventive concept will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the inventive concept are shown. The advantages and features of theinventive concept and methods of achieving them will be apparent fromthe following exemplary embodiments that will be described in moredetail with reference to the accompanying drawings. It should be noted,however, that the inventive concept is not limited to the followingexemplary embodiments, and may be implemented in various forms.Accordingly, the exemplary embodiments are provided only to disclose theinventive concept and let those skilled in the art know the category ofthe inventive concept. In the drawings, embodiments of the inventiveconcept are not limited to the specific examples provided herein and areexaggerated for clarity.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to limit the invention. As usedherein, the singular terms “a,” “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. It will beunderstood that when an element is referred to as being “connected” or“coupled” to another element, it may be directly connected or coupled tothe other element or intervening elements may be present.

Similarly, it will be understood that when an element such as a layer,region or substrate is referred to as being “on” another element, it canbe directly on the other element or intervening elements may be present.In contrast, the term “directly” means that there are no interveningelements. It will be further understood that the terms “comprises”,“comprising,”, “includes” and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Additionally, the embodiment in the detailed description will bedescribed with sectional views as ideal exemplary views of the inventiveconcept. Accordingly, shapes of the exemplary views may be modifiedaccording to manufacturing techniques and/or allowable errors.Therefore, the embodiments of the inventive concept are not limited tothe specific shape illustrated in the exemplary views, but may includeother shapes that may be created according to manufacturing processes.Areas exemplified in the drawings have general properties, and are usedto illustrate specific shapes of elements. Thus, this should not beconstrued as limited to the scope of the inventive concept.

It will be also understood that although the terms first, second, thirdetc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another element. Thus, a first element insome embodiments could be termed a second element in other embodimentswithout departing from the teachings of the present invention. Exemplaryembodiments of aspects of the present inventive concept explained andillustrated herein include their complementary counterparts. The samereference numerals or the same reference designators denote the sameelements throughout the specification.

Moreover, exemplary embodiments are described herein with reference tocross-sectional illustrations and/or plane illustrations that areidealized exemplary illustrations. Accordingly, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances, are to be expected. Thus, exemplaryembodiments should not be construed as limited to the shapes of regionsillustrated herein but are to include deviations in shapes that result,for example, from manufacturing. For example, an etching regionillustrated as a rectangle will, typically, have rounded or curvedfeatures. Thus, the regions illustrated in the figures are schematic innature and their shapes are not intended to illustrate the actual shapeof a region of a device and are not intended to limit the scope ofexample embodiments.

Hereinafter, embodiments of the inventive concept will be described indetail with reference to the drawings.

Light Emitting Device, First Embodiment

FIG. 1 is a plan view illustrating a light emitting device according toembodiments of the inventive concept. FIG. 2A is a cross-sectional viewillustrating a light emitting device according to some embodiments ofthe inventive concept. FIG. 2A a cross-sectional view taken along a lineI-I′ of FIG. 1. FIG. 2B is a cross-sectional view illustrating a path oflight generated from a light emitting device according to someembodiments of the inventive concept.

Referring to FIGS. 1 and 2A, a light emitting device may include atransparent substrate 100, a first transparent electrode 102, a secondtransparent electrode 110, an organic light emitting layer 108, anassistant electrode 106, and a light path changing structure 112.

Referring to FIG. 1, the light emitting device may include a firstregion and a second region. The first region may correspond to a lighttransmission region and the second region may correspond to a lightnon-transmission region. The first region may be surrounded by thesecond region in a plan view. For example, the first region may have aquadrilateral shape and the second region may have a mesh-shapesurrounding the first region when the light emitting device is viewedform a top view.

Referring to FIGS. 1 and 2A, the first and second transparent electrodes102 and 110, the organic light emitting layer 108, and the transparentsubstrate 100 may completely cover the first and second regions. But,the assistant electrode 106 and the light path changing structure 112may mask the second region selectively.

Referring to FIG. 2A, the transparent substrate 100 may be a glasssubstrate or a plastic substrate. The first transparent electrode 102may be disposed on a first surface of the transparent substrate 100. Thelight path changing structure 112 may be disposed on a second surface ofthe transparent substrate 100 of the second region.

The first transparent electrode 102 may be formed of indium tin oxide(ITO) or indium zinc oxide (IZO) having excellent light transmittance.The first transparent electrode 102 may function as an anode supplyingholes into the organic light emitting layer 108.

The second transparent electrode 110 may face one surface of the firsttransparent electrode 102 and be spaced apart from the one surface ofthe first transparent electrode 102. The second transparent electrode110 may be formed of a metal thin film having light transmittance and alow work function of about 4.5 eV or less. For example, the secondtransparent electrode 110 may be formed of aluminum (Al), silver (Ag),molybdenum (Mo), and/or copper (Cu). The second transparent electrode110 may function as a cathode supplying electrons into the organic lightemitting layer 108.

The organic light emitting layer 108 may be disposed between the firstand second transparent electrodes 102 and 110. In some embodiments, onesurface of the organic light emitting layer 108 may include a firstportion in contact with the first transparent electrode 102 in the firstregion, and a second portion spaced apart from the first transparentelectrode 102 in the second region. In other words, the one surface ofthe organic light emitting layer 108 may have a stepped shape due to thefirst and second portions thereof. Another surface of the organic lightemitting layer 108 may be fully in contact with the second transparentelectrode 110.

The organic light emitting layer 108 may correspond to an organicelectro luminescence layer. The organic light emitting layer 108 mayinclude at least one layer generating light. Even though not shown indetail in the drawings, in some embodiments, the organic light emittinglayer 108 may include a hole-transport layer, a light emitting layer,and an electron-transport layer. The light emitting layer may include aplurality of light emitting layers including a blue light emittinglayer, a green light emitting layer, and a red light emitting layer.

The assistant electrode 106 may be disposed between the first and secondtransparent electrodes 102 and 110. In some embodiments, the assistanceelectrode 106 may be disposed between the organic light emitting layer108 and the first transparent electrode 102 in the second region. Inother words, the assistant electrode 106 may be disposed between thefirst transparent electrode 102 of the second region and the secondportion of the one surface of the organic light emitting layer 108 whichconstitutes the stepped shape. The organic light emitting layer 108 maybe in contact with the first transparent electrode 102 in the firstregion and the assistant electrode 106 in the second region.

The assistant electrode 106 may be formed of a metal having a resistancelower than that of the first transparent electrode 102. Additionally,the assistant electrode 106 may be formed of a metal which light doesnot pass through. For example, the assistant electrode 106 may be formedof chromium (Cr). The assistant electrode 106 may improve non-uniformityof luminance which may be caused by voltage drop of the light emittingdevice.

The light path changing structure 112 may be disposed on the secondsurface of the transparent substrate 100. Here, the light path changingstructure 112 may selectively mask the second region. In someembodiment, the light path changing structure 112 may include a microlens array MLA. In some embodiments, the micro lens array MLA may bearranged to mask the second region.

Referring to FIG. 2B, the light path changing structure 112 may change apath of light which is emitted from the organic light emitting layer 108and then passes through the transparent substrate 100.

Since the light path changing structure 112 is selectively applied toonly the second region in which the assistant electrode 106 is disposed,the light path changing structure 112 may not influence alight-transmittance of the light emitting device. A part of the lightoutputted from the transparent substrate 100 may be laterally lost bytotal reflection. However, the part of the light may be laterally lostmay proceed toward the front of the light emitting device due to thelight path changing structure 112. Thus, a light output efficiency ofthe light emitting device may be improved by about 10% to about 20%.

Additionally, the light emitting device may further include a sealingsubstrate 116 covering the second transparent electrode 110. The sealingsubstrate 116 may perform a function that protects the light emittingdevice.

An operation method of the light emitting device will be describedbriefly. A voltage may be applied between the first and secondtransparent electrodes 102 and 110. Thus, for example, electronsprovided from the second transparent electrode 110 functioning as thecathode may be combined with holes provided from the first transparentelectrode 102 functioning as the anode, so that excitons may be formed.The excitons may be radiatively recombined to generate light.

Light Emitting Device, Second Embodiment

FIG. 3A is a cross-sectional view illustrating a light emitting deviceaccording to other embodiments of the inventive concept. FIG. 3A is across-sectional view taken along a line I-I′ of FIG. 1. FIG. 3B is across-sectional view illustrating a path of light generated from a lightemitting device according to other embodiments of the inventive concept.

Referring to FIGS. 1 and 3A, a light emitting device may include atransparent substrate 100, a first transparent electrode 102, a secondtransparent electrode 110, an organic light emitting layer 108, anassistant electrode 106, a light path changing structure 112, and asealing substrate 116.

The transparent substrate 100 may include a first surface in contactwith the first transparent electrode 102 and a second surface oppositeto the first surface.

In some embodiment, the light path changing structure 112 may include apattern P which is formed at the transparent substrate 100 of the secondregion. In some embodiments, the pattern P may have concave-curvedsurfaces lower than the second surface of the transparent substrate 100of the first region.

Referring to FIG. 3B, the light path changing structure 112 may change apath of light which is emitted from the organic light emitting layer 108and then passes through the transparent substrate 100.

Since the light path changing structure 112 including the pattern P isselectively applied to only the second region in which the assistantelectrode 106 is disposed, the light path changing structure 112 may notinfluence a light-transmittance of the light emitting device.Additionally, the part of the light may be laterally lost by the totalreflection may proceed toward the front of the light emitting device dueto the light path changing structure 112. Thus, a light outputefficiency of the light emitting device may be improved by about 10% toabout 20%.

The transparent substrate 100, the first transparent electrode 102, thesecond transparent electrode 110, the organic light emitting layer 108,the assistant electrode 106, and the sealing substrate 116 may besubstantially the same as the transparent substrate 100, the firsttransparent electrode 102, the second transparent electrode 110, theorganic light emitting layer 108, the assistant electrode 106, and thesealing substrate 116 which are described with reference to FIG. 2A.Thus, descriptions thereof will be omitted.

Light Emitting Device, Third Embodiment

FIG. 4A is a cross-sectional view illustrating a light emitting deviceaccording to still other embodiments of the inventive concept. FIG. 4Ais a cross-sectional view taken along a line I-I′ of FIG. 1. FIG. 4B isa cross-sectional view illustrating a path of light generated from alight emitting device according to still other embodiments of theinventive concept.

The transparent substrate 100 may include a first surface in contactwith the first transparent electrode 102 and a second surface oppositeto the first surface.

In some embodiments, the light path changing structure 112 may includean optical dispersion layer OD masking the transparent substrate 100 ofthe second region. The optical dispersion layer OD may includenano-particles.

Referring to FIG. 4B, the light path changing structure 112 may change apath of light which is emitted from the organic light emitting layer 108and then passes through the transparent substrate 100.

Since the light path changing structure 112 including the opticaldispersion layer OD is selectively applied to only the second region inwhich the assistant electrode 106 is disposed, the light path changingstructure 112 may not influence a light-transmittance of the lightemitting device. Additionally, the part of the light may be laterallylost by the total reflection may proceed toward the front of the lightemitting device due to the light path changing structure 112. Thus, alight output efficiency of the light emitting device may be improved byabout 10% to about 20%.

The transparent substrate 100, the first transparent electrode 102, thesecond transparent electrode 110, the organic light emitting layer 108,the assistant electrode 106, and the sealing substrate 116 may besubstantially the same as the transparent substrate 100, the firsttransparent electrode 102, the second transparent electrode 110, theorganic light emitting layer 108, the assistant electrode 106, and thesealing substrate 116 which are described with reference to FIG. 2A.Thus, descriptions thereof will be omitted.

Method of Manufacturing Light Emitting Device, First Embodiment

FIGS. 5A to 5G are cross-sectional views illustrating a method ofmanufacturing a light emitting device according to some embodiments ofthe inventive concept.

Referring to FIG. 5A, a first transparent electrode 102 and an assistantelectrode layer 104 may be sequentially stacked on a first surface of atransparent substrate 100.

The transparent substrate 100 may include a first region and a secondregion. The first region may correspond to a light transmission regionand the second region may correspond to a light non-transmission region.The first transparent electrode 102 and the assistant electrode layer104 may be formed to completely cover the first surface of thetransparent substrate 100.

The first transparent electrode 102 may be formed of an ITO layer and/oran IZO layer. The assistant electrode layer 104 may include a metal suchas chromium (Cr).

Referring to FIG. 5B, the assistant electrode layer 104 may beselectively etched to form an assistant electrode 106 masking the secondregion. At this time, the first transparent electrode 102 of the firstregion may be exposed.

Referring to FIG. 5C, an organic light emitting layer 108 may be formedon the first transparent electrode 102 which the assistant electrode 106is formed on. The organic light emitting layer 108 may be formed by athermal evaporation process.

Even though not shown in detail in the drawings, a hole-transport layer,a light emitting layer, and a electrode-transport layer may besequentially stacked to form the organic light emitting layer 108.Additionally, the light emitting layer may include a plurality of lightemitting layers including a blue light emitting layer, a green lightemitting layer, and a red light emitting layer.

Referring to FIG. 5D, a second transparent electrode 110 may be formedon the organic light emitting layer 108. The second transparentelectrode 110 may include a metal thin film having light transmittanceand a low work function of about 4.5 eV or less. For example, the secondtransparent electrode 110 may be formed of aluminum (Al), silver (Ag),molybdenum (Mo), and/or copper (Cu).

Referring to FIG. 5E, a transfer substrate 114 including a micro lensarray MLA bonded on one surface thereof may be prepared.

The micro lens array MLA may be fixed to the transfer substrate 114 byan adhesive layer which is detachable by heat. Additionally, the microlens array MLA may be disposed to be aligned with the second region.

Referring to FIG. 5F, the micro lens array MLA may be fixed on a secondsurface of the transparent substrate 100 in the second region, therebyforming a light path changing structure 112. The second surface of thetransparent substrate 100 may be opposite to the first surface thereof.

In some embodiments, the light path changing structure 112 may be formedin a film-shape including the micro lens array MLA.

Since the light path changing structure 112 including the micro lensarray MLA is selectively applied to only the second region in which theassistant electrode 106 is disposed, the light path changing structure112 may not influence a light-transmittance of the light emittingdevice. Additionally, the part of the light may be laterally lost by thetotal reflection may proceed toward the front of the light emittingdevice by the light path changing structure 112. Thus, a light outputefficiency of the light emitting device may be improved by about 10% toabout 20%.

Referring to FIG. 5G, a sealing substrate 116 may be formed to cover thesecond transparent electrode 110.

In more detail, the second transparent electrode 110 may include a firstsurface in contact with the organic light emitting layer 108 and asecond surface opposite to first surface. The sealing substrate 116 maybe formed on the second surface of the second transparent electrode 110.

Method of Manufacturing Light Emitting Device, Second Embodiment

FIGS. 6A to 6D are cross-sectional views illustrating a method ofmanufacturing a light emitting device according to other embodiments ofthe inventive concept.

Referring to FIG. 6A, a transparent substrate 100 may include a firstsurface and a second surface opposite to the first surface. A firsttransparent electrode 102 and an assistant electrode layer 104 may besequentially formed on the first surface of the transparent substrate100. The transparent substrate 100 may include a first regioncorresponding to a light transmission region and a second regioncorresponding to a light non-transmission region.

Referring to FIG. 6B, the second surface of the transparent substrate100 in the second region may be selectively etched to form a pattern Phaving concave-curved surfaces lower than the second surface of thetransparent substrate 100 in the first region. Thus, a light pathchanging structure 112 having the pattern P may be formed. Thetransparent substrate 100 may be etched by a wet etching process.

Referring to FIG. 6C, an assistant electrode 106, an organic lightemitting layer 108, and a second transparent electrode 110 may be formedon the first surface of the transparent substrate 100 which the firsttransparent electrode 102 is formed on.

In more detail, the assistant electrode layer 104 on the firsttransparent electrode 102 may be etched to form the assistant electrode106 selectively masking the second region of the transparent substrate100. The organic light emitting layer 108 and the second transparentelectrode 110 may be sequentially formed to cover the assistantelectrode 106 and the first transparent electrode 102.

Referring to FIG. 6D, a sealing substrate 116 may be formed to cover thesecond transparent electrode 110. In more detail, the second transparentelectrode 110 may include a first surface in contact with the organiclight emitting layer 108 and a second surface opposite to first surface.The sealing substrate 116 may be formed on the second surface of thesecond transparent electrode 110.

Thus, the light emitting device including the light path changingstructure 112 may be manufactured. Since the light path changingstructure 112 including the pattern P is selectively applied to only thesecond region in which the assistant electrode 106 is disposed, thelight path changing structure 112 may not influence alight-transmittance of the light emitting device. Additionally, the partof the light may be laterally lost by the total reflection may proceedtoward the front of the light emitting device by the light path changingstructure 112. Thus, a light output efficiency of the light emittingdevice may be improved by about 10% to about 20%.

Method of Manufacturing Light Emitting Device, Third Embodiment

FIGS. 7A and 7B are cross-sectional views illustrating a method ofmanufacturing a light emitting device according to still otherembodiments of the inventive concept.

Referring to FIG. 7A, a first transparent electrode 102 and an assistantelectrode layer 140 may be sequentially formed on a first surface of atransparent substrate 100 including a first region corresponding to alight transmission region and a second region corresponding to a lightnon-transmission region. An optical dispersion layer OD may be adheredto a second surface of the transparent substrate 100. The opticaldispersion layer OD may cover the second region. Thus, a light pathchanging structure 112 including the optical dispersion layer OD may beformed.

Referring to FIG. 7B, the assistant electrode layer 104 may be patternedto form an assistant electrode 106. And then an organic light emittinglayer 108, a second transparent electrode 110, and a sealing substrate116 may be formed. Descriptions thereof may be substantially the same asdescribed with reference to FIGS. 6C and 6D.

According to embodiments of the inventive concept, since the light pathchanging structure is selectively applied to only the second region inwhich the assistant electrode 106 is disposed, the light path changingstructure may not influence a light-transmittance of the light emittingdevice. Additionally, the part of the light may be laterally lost by thetotal reflection may proceed toward the front of the light emittingdevice by the light path changing structure. Thus, the light outputefficiency of the light emitting device may be improved.

While the inventive concept has been described with reference to exampleembodiments, it will be apparent to those skilled in the art thatvarious changes and modifications may be made without departing from thespirit and scope of the inventive concept. Therefore, it should beunderstood that the above embodiments are not limiting, butillustrative. Thus, the scope of the inventive concept is to bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing description.

What is claimed is:
 1. A light emitting device comprising: a transparentsubstrate including a first region and a second region on substantiallya same plane as the first region; a first transparent electrode disposedon a first surface of the transparent substrate; a second transparentelectrode facing and spaced apart from the first transparent electrode;an organic light emitting layer disposed between the first and secondtransparent electrodes; an assistant electrode disposed between thefirst and second transparent electrodes, the assistant electrodeselectively masking the second region; and a light path changingstructure disposed on a second surface of the transparent substrate, thelight path changing structure selectively masking the second region,wherein the light path changing structure overlaps the assistantelectrode in a plane view.
 2. The light emitting device of claim 1,wherein the light path changing structure includes a micro lens array.3. The light emitting device of claim 1, wherein the light path changingstructure includes a pattern formed at the transparent substrate in thesecond region.
 4. The light emitting device of claim 3, wherein thepattern formed at the transparent substrate has concave-curved surfaces.5. The light emitting device of claim 1, wherein the light path changingstructure includes an optical dispersion layer.
 6. The light emittingdevice of claim 5, wherein the optical dispersion layer includesnano-particles.
 7. The light emitting device of claim 1, wherein theassistant electrode includes a metal which light does not pass throughand which has a resistance lower than that of the first transparentelectrode.
 8. A light emitting device comprising: a transparentsubstrate including a first region and a second region; a firsttransparent electrode disposed on a first surface of the transparentsubstrate; a second transparent electrode facing and spaced apart fromthe first transparent electrode; an organic light emitting layerdisposed between the first and second transparent electrodes; anassistant electrode disposed between the first and second transparentelectrodes, the assistant electrode selectively masking the secondregion; and a light path changing structure disposed on a second surfaceof the transparent substrate, the light path changing structureselectively masking the second region, wherein the light path changingstructure does not dispose on the first region of the transparentsubstrate, wherein the assistant electrode does not mask the firstregion of the transparent substrate.